INTRODUCTION The Research Participation Core (RPC) has been in existence since 1990. Although the RPC was reviewed quite favorably in the last competitive renewal, receiving a descriptor of "High Outstanding," the Core has, by design, changed significantly during the present project period. Technological, empirical, and theoretical advances are occurring at a rapid rate in many of the disciplines in which MRDDRC investigators work. In order to provide the resources and services necessary to support the cutting-edge research efforts of MRDDRC investigators, the RPC continuously evaluates its services and endeavors to anticipate advances in the field and new directions in the research of MRDDRC investigators. This section describes the rationale for the RPC, the services it provides, the resources it draws on, and examples of its impact on the science conducted within the MRDDRC, as well as the changes that have occurred since the last competitive renewal.